Transcription-driven cohesin accumulation is associated with secretory phenotype of senescence [HiC]

Senescence is a stable form of cell cycle arrest that is triggered in response to various pathophysiological stimuli. The three-dimensional structure of senescent cells has been previously characterised, mostly in terms of macro-domains or changes between large heterochromatic regions. In the present body of work, using a combination of HiC and targetted Capture Hi-C, we aimed to investigate the association between gene expression and local chromatin structure in senescence, particularly focusing on enhancer-promoter (EP) interactions. We show that many EP contacts are rewired in RAS-induced Senescence compared to 'normal', growing cells and that these are associated with cohesin binding changes and possible loop re-organisation. The genes affected by altered chromatin interactions correspond to the two main axes of senescence gene regulation: cell cycle and inflammation. Our findings are potentially relevant during ageing and in cancers with cohesin mutations, where cell cycle and inflammation are also deregulated. Overall design: HiC and Capture HiC of growing and (RAS-induced) senescent IMR90 fibroblasts